An article by 6 teams of respected modellers, published in Reviews of Geophysics, claims that it has ruled out the extreme scenarios of climate change (https://www.theguardian.com/environment/2020/jul/22/global-heating-study-narrows-range-of-probable-temperature-rises). The authors point out that when the climate change debate got seriously underway, it was predicted that an increase in atmospheric concentrations of carbon dioxide to 280 parts per million (ppm) from pre-industrial levels, carried a 66% risk of heating the planet by between 1.5⁰C (deemed to be manageable) and 4.5⁰C (deemed to be catastrophic). Their new models suggest that the 66% probability will actually generate planetary temperature increases of between 2.6 and 3.9⁰C (which both seem pretty bad to me). Their study further points out that, in May 2020, atmospheric carbon dioxide was 417 ppm and was increasing by 2.5 ppm/year. In fairness, the authors do reiterate that we have no room for complacency and still urge that drastic efforts should be made to curb 'greenhouse gases'. I am not, however, very reassured by their upper prediction being somewhat lower than that claimed in the initial studies (the upper and the lower limits are both likely to have very unpleasant consequences). It's a bit like saying 'Good news. You will only be shot dead, using a smaller calibre bullet!'
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